Natural Circulation Solar Water Heater
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Components of Natural circulation solar water heater:-

1) Flat plate collector (i.Transparent cover ii. Insulating material iii. Casing iv. Stand)
2) Insulated water storage tank
3) Insulated water circulation system
4) Auxiliary heating system

Theory:-

It is a very simple natural circulation system consists of a tilted flat plate collector with transparent cover plates, highly insulated water storage tank and insulated pipe connecting the collector and storage tank. The bottom of the tank is at least 1 ft (0.3 m) higher than the top of the collector and the circulation occurs through the natural convection.

When water in the collector is heated by the sun, it expands due to decrease of its density; hence it rises and flows into the top of the storage tank. Due to the density difference colder water enter the lower heater of the collector for further heating. This procedure continues throughout the sunshine hour.

After sunset, natural convection system can act reverse flow direction. To avoid this flow the top of the absorber (heater) should be at least 1 foot (0.3 m) below the bottom of the storage tank.

To supply heat during long cloudy periods, an electrical immersion heater can be used as a backup of the solar system.


Conclusions:-

It is a simple water heating system, which do not require mechanical pump to circulate the water. This type of water heater is very popular in rural areas, where the electricity is expensive or not available and there is no risk of freezing.


Solar Water Heater